1. Field of the Invention
This invention generally relates to apparatus for brewing beverages by directing a liquid, such as hot water, across a compacted infusible material, such as ground coffee beans, in a sealed infusion chamber.
2. Description of Related Art
A large number of commercial devices are available for brewing beverages, particularly coffee, by infusing material with a liquid. Prior art coffee makers have incorporated a variety of percolating, drip, steeping and other brewing approaches. A large number of these coffee makers were also designed to brew coffee in batches, for example, 4-cup to 12-cup batches. Such devices, however, were characterized by difficulties in maintaining coffee flavor over time, in controlling waste as occurred by making excessive coffee that was then discarded, and in cleaning and maintenance of the coffee makers.
The advent of espresso machines introduced new coffee brewing concepts. Espresso machines produce a small quantity of coffee at any given time, such as a cup of cappuccino or espresso. Espresso was brewed and continues to be brewed by placing an appropriate quantity of ground espresso coffee into an infusion chamber, compacting the ground coffee and closing that chamber. Hot water under pressure infuses the compacted coffee to extract its essence and directs the beverage to a cup.
This process has become very popular, and there are a variety of implementations primarily for use in espresso machines, but also for machines for brewing coffee. For example, U.S. Pat. No. 4,457,216 to Dremmel discloses an infusion chamber with hydraulically operated upper and lower pistons that close a scalding chamber. The scalding chamber contains coffee grounds and receives hot water. During the brewing process the loose coffee swells. When brewing is complete, the lower piston rises to compress the swollen grounds extract the brewed coffee that passes through the lower piston to a cup or other serving receptacle. After the brewing cycle is complete, the upper piston retracts. Then the lower piston can elevate to position the used compressed coffee grounds above the infusion chamber for removal.
U.S. Pat. Nos. 4,796,521 and 5,255,594 to Grossi disclose infusion chambers with a piston that delivers hot water by means of a metering unit. The piston is operated to allow the introduction of a filter carrier element and for compressing the coffee powder. U.S. Pat. No. 4,796,521 discloses a direct introduction of ground coffee from a coffee grinder into the infusion chamber. U.S. Pat. No. 5,255,594 discloses a motor drive.
U.S. Pat. No. 5,230,277 to Bianco discloses two pistons mounted on circulating ball screw actuators for closing the top and bottom of an infusion chamber. The pistons are brought together to compact ground coffee after which hot water is introduced for infusion. After the brewing cycle, both pistons can be raised so the lower piston can eject the used coffee grounds.
In U.S. Pat. No. 5,237,911 to Aebi a piston moves into an infusion chamber to compress ground coffee. The bottom of the piston comes into direct contact with the compressed ground coffee. There is no specific disclosure of a seal for preventing the escape of water from the infusion chamber past the piston.
U.S. Pat. No. 5,277,102 to Martinez discloses a vending machine with a lower piston. The lower piston rises to compact ground coffee against a fixed upper plunger or piston.
In U.S. Pat. No. 5,280,747 to Bonneville an espresso machine has a vertically movable snout for supplying hot water under pressure to ground coffee held in a filter. A cylinder or piston moves against the action of an antagonist spring to cause the snout to penetrate the package and compress the ground coffee.
U.S. Pat. No. 5,302,407 to Vetterli discloses a brewing or infusion chamber with a movable piston. The brewing chamber has an open top. A closure piston opens and closes the brewing chamber. Pressurized hot water causes the movable piston to move upward to compress the ground coffee.
In U.S. Pat. No. 5,402,706 to Locati an infusion chamber has a lower filter piston and an upper, two-part infuser piston. The infuser piston has a seal. One part of the upper piston slides into the other part against an opposing spring resistance. The seal remains in a contracted condition at a narrow diameter of a conical seat while the infusion piston enters the infusion chamber. During an operating stage, however, the distance between the two portions of the piston decreases causing the seal to shift upward to a maximum diameter of a conical seat. This process provides a seal and eliminates brushing and scraping of the packing to minimize wear and tear.
U.S. Pat. No. 5,911,810 to Kawabata discloses a coffee brewing system in which a vertically movable cylinder receives ground coffee and has a top opening. A vertically movable, upwardly urged plunger compacts grounds after second cylinder is elevated.
U.S. Pat. No. 6,035,762 to Ruckstuhl discloses an espresso machine with a brewing chamber in which two brewing chamber parts can be displaced relative to one another. In a closed position they form a brewing chamber for filter capsules. One of the members has multiple nozzles for directing hot water across the coffee. This approach allows the use of coffee pods of different sizes.
In U.S. Pat. No. 6,606,938 to Taylor, a beverage brewing apparatus includes a disposable cartridge that is initially pierced and vented by a tubular outlet probe when an arm pivots a water disposing head into a sealing relationship with the top of the removable cartridge.
U.S. Pat. No. 6,711,988 discloses an espresso machine with a variable volume infusion chamber. A piston with a static seal, shown as an O-ring, seals against and moves relative to an infusion cylinder. During brewing the piston elevates underwater pressure to allow swirling. When a predetermined pressure is obtained, a frothing valve opens. The piston moves toward the frothing valve to press the coffee grounds under a spring-generated force.
These and other features have been incorporated in a number of single-cup coffee makers, particularly for espresso machines for commercial use, as in restaurants, coffee shops and the like. However, such machines are expensive and not economically attractive to most consumers even though they may make the best coffee.
Recently several manufactures have introduced so-called “cup-at-a-time” coffee makers. They replace such pistons with hinged top units that latch to a base. A consumer must manually unlatch the hinged top unit, open it to expose a container for receiving either proprietary coffee pods or loose coffee. Then the consumer must manually close and latch the top unit to compact the coffee and form the sealed infusion chamber.
With cup-at-a-time coffee makers clean up requires the top to be reopened. If the coffee is made with loose grounds, the grounds cup must be removed so the used grounds can be discarded. If a pod is used, it can be lifted from a grounds cup without having to remove the grounds cup.
In many applications consumers desire automatic systems that incorporate coffee grinders. Such systems are characterized by locating the brewing chamber at an inaccessible location so it becomes impossible or, at best, very difficult, to clean the brewing chamber. Cleaning the brewing chamber in any such coffee maker is very important. If regular cleaning is not undertaken, oils and organic acids present in coffee attack the seal materials used to define the brewing chamber. Such substances also accumulate on the walls of the brewing chamber. If the seal slides over the walls, this material produces a rough surface that can damage the seals with use.
Some commercially available consumer-oriented coffee makers limit the consumer to proprietary prepackaged coffee filter pods. This can limit consumer choices. Also some consumer-oriented coffee makers are limited to making espresso. These factors and expense limit their market to consumers.
What is needed is apparatus for brewing a beverage, such as coffee, that is economical and easy to use. Specifically, what is needed is an economical coffee brewing apparatus that eliminates manual operation of latches, facilitates the incorporation of a grinder, simplifies cleaning and maintenance and is adapted for accepting ground coffee in a variety of forms.